AUTHOR=Fauvet Bruno , Finka Andrija , Castanié-Cornet Marie-Pierre , Cirinesi Anne-Marie , Genevaux Pierre , Quadroni Manfredo , Goloubinoff Pierre 

TITLE=Bacterial Hsp90 Facilitates the Degradation of Aggregation-Prone Hsp70–Hsp40 Substrates

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2021.653073

DOI=10.3389/fmolb.2021.653073

ISSN=2296-889X

ABSTRACT=<p>In eukaryotes, the 90-kDa heat shock proteins (Hsp90s) are profusely studied chaperones that, together with 70-kDa heat shock proteins (Hsp70s), control protein homeostasis. In bacteria, however, the function of Hsp90 (HtpG) and its collaboration with Hsp70 (DnaK) remains poorly characterized. To uncover physiological processes that depend on HtpG and DnaK, we performed comparative quantitative proteomic analyses of insoluble and total protein fractions from unstressed wild-type (WT) <italic>Escherichia coli</italic> and from knockout mutants Δ<italic>dnaKdnaJ</italic> (ΔKJ), Δ<italic>htpG</italic> (ΔG), and Δ<italic>dnaKdnaJ</italic>Δ<italic>htpG</italic> (ΔKJG). Whereas the ΔG mutant showed no detectable proteomic differences with wild-type, ΔKJ expressed more chaperones, proteases and ribosomes and expressed dramatically less metabolic and respiratory enzymes. Unexpectedly, we found that the triple mutant ΔKJG showed higher levels of metabolic and respiratory enzymes than ΔKJ, suggesting that bacterial Hsp90 mediates the degradation of aggregation-prone Hsp70–Hsp40 substrates. Further <italic>in vivo</italic> experiments suggest that such Hsp90-mediated degradation possibly occurs through the HslUV protease.</p>